Inspired by the fictional Dr. Heiter, disturbed loner Martin dreams of creating a 12-person centipede and sets out to realize his sick fantasy.
Martin is a mentally disturbed loner who lives with his mother in a bleak housing project. He works the night shift as a security guard in an equally grim and foreboding underground parking complex. To escape his dreary existence, Martin loses himself in the fantasy world of the cult horror film The Human Centipede (First Sequence) (2009), fetishizing the meticulous surgical skills of the gifted Dr. Heiter, whose knowledge of the human gastrointestinal system inspires Martin to attempt the unthinkable.—six entertainment company
The film opens with the final credits of The Human Centipede (First Sequence), including the closing credits. The camera pulls back, to reveal that this is playing on a portable DVD player, and a man in a toll booth in a parking garage is watching the film. Martin Lomax (Laurence R. Harvey) is an asthmatic, overweight, mentally ill, middle-aged, short British man. He lives in a small flat with his emotionally abusive mother (Vivien Bridson) while working as a security guard in an underground parking garage. His neighbors play punk music at high levels all night and day, and Martin often spies on the rich individuals who use the parking garage. Dr. Sebring (Bill Hutchens) suspects that Martin was sexually abused repeatedly by his father, now in prison (a suspicion confirmed when Martin has a flashback to this abuse, in which the audience hears the father raping his son).
In a metanarrative device, Martin is obsessed with the movie The Human Centipede (First Sequence), watching it repeatedly at home and in his toll booth. At one point, he is depicted masturbating to the film with sandpaper wrapped around his penis. He keeps a centipede as a pet, and maintains a scrapbook on the film. When his mother finds and destroys the scrapbook, Martin kills her by bashing her head in and then props her dead body up at the kitchen table. Martin wordlessly decides to recreate the fictional experiment he saw portrayed in The Human Centipede (First Sequence). Medically untrained, he assembles a potpourri of kitchen gadgets, woodworking tools, and assorted household items, puts them in a suitcase, and secures a dingy, dirty, dark abandoned warehouse to recreate the film's medical experiment. But Martin intends to create not just a three-person centipede, but the "full sequence" of 12 connected people.
He telephones the three actors from the first film, pretending to be Quentin Tarantino's casting agent, and tries to lure them to London. Only one, Ashlynn Yennie (portraying herself), does so. Most of the first hour of the film shows how Martin attacks, beats, and kidnaps his victims. Among his victims are a neighbor, a rental agent, and a man and his very pregnant wife. Once Martin has his victims, he severs the tendons in each person's legs (graphically and on screen) to prevent them from fleeing. He uses a hammer to knock out their teeth one by one, putting his fingers in their blood-filled mouths to fish out their teeth so they will not swallow and choke on them in a suicide attempt. He slices open the buttocks of 11 of the victims (graphically depicted on screen), and then, lacking any surgical equipment, uses a staple gun to attach each person's face to the next person's anus. Martin chooses Yennie to be the front of the "human centipede," so she does not have to eat anyone else's feces. Finally, Martin has his full sequence of a 12-person "human centipede". When one of his victims dies from their wounds, Martin sobs softly.
Martin (who is clad only in his underwear throughout much of the latter portion of the film) becomes more and more sexually aroused by the desperation and travails of his "human centipede." He administers an excessive amount of laxative to his creation, forcing each individual in the chain to explosively evacuate their bowels into the mouth of the person behind them. When one of his victims chokes to death on their own vomit, Martin again breaks down in tears.
Unbeknownst to Martin, the pregnant woman whom he believed had died regains consciousness under a tarp next to another dead body. She bursts out of the tarp and runs outside, screaming, and leaps into her car and drives off. Martin chases after her and throws himself against the car's windows, unable to get in. At the same time, the pregnant woman driving goes into labor and births a child into the foot well. Immediately after, the engine turns over and she stomps on the accelerator, smashing her newborn's skull in the process. Martin is shown crying in rage.
Meanwhile, the "centipede" splits in half as one of the victim rips his face from the person in front. Martin then returns to the warehouse and shoots all the remaining eight members of the centipede in rage until his gun runs out of ammo. He decides to put his victims out of their misery by slicing their necks with a kitchen knife. Miss Yennie is the only member that remains alive. When Martin approaches her to slice her neck, she punches him in the groin then, in a fit of adrenalin-induced rage, she grabs the funnel Martin used to force feed her earlier, shoves it up Martin's rectum, grabs the centipede from his glass cage and sticks it inside. Yennie is then stabbed in the face by Martin and presumably dies. Martin is then shown screaming as he tries to remove the centipede. As he staggers out the door, the camera focuses on the dead centipede and Ashlynn Yennie is shown turning over of her own accord, possibly hinting that she survived.
The final shot shows Martin, alive and well, watching the DVD of the original film at work, while a baby is heard crying in the background. (It may be that Human Centipede (Full Sequence) was merely a dream, or it may be that Martin has returned to his job and is now planning further crimes.)
